1. Field of the Invention
This invention relates to a plant for the continuous casting of steel, wherein molten steel is vertically cast in mold means to form a strand having an elongate shape in cross-section and is caused to solidify as it flows through the mold means
2. Description of the Prior Art
In the conventional continuous casting processes using stationary molds, only low casting speeds of about 1.5 to 5 meters per minute can be achieved and only relatively short molds having a length of about 900 mm can be used because heat must be dissipated at a high rate through the mold so that an intense contact between the strand and the mold will be required, on the one hand, and because optimum friction conditions must be ensured owing to the sliding movement of the strand within the mold and the fact that the strand shell still has only a low strength. To achieve economically satisfactory casting rates in spite of such rather restricting requirements, the strands must have a large thickness, e.g., of 210 mm. For this reason the slabs or blooms produced by such continuous casting processes must greatly be reduced in cross-section during their subsequent further processing to produce a broad strip having a thickness of only a few millimeters and expensive plants are required for that purpose. Known traveling molds in which a relative movement between the strand and the mold wall is avoided permit a higher casting speed than stationary molds so that a given casting rate can be achieved with strands having a reduced thickness down to about 100 to 150 mm. But the dimensions of conventional pouring pipes require the mold to have a sufficiently large entrance cross-section and do not permit a casting of strands having a smaller thickness without the use of a reducing mold. For this reason even the slabs which can be produced by means of a traveling mold having a constant cavity cross-section are too thick and a more effective rationalization of the further processing is prevented.
Stationary molds having a reducing cavity have also been provided in order to make thin slabs but the small entrance cross-section requires the use of special pouring funnels and the strand leaving the mold has only a thin shell, which must be supported and cooled by special means. Besides, that mold does not permit casting speeds to be achieved which would permit an immediate feeding of the thin slabs to a rolling mill train.
It has been proposed to provide for a continuous casting of flat slabs having a thickness of about 50 mm a reducing mold which consists of a traveling plate mold consisting of converging plate chains so that the strand is reduced in cross-section from a large entrance cross-section conforming to the dimensions of the casting pipe to a correspondingly smaller exit cross-section as the strand passes through the mold. Whereas that reducing mold can be used to make relatively thin slabs under conventional casting conditions, the casting speeds which can be achieved are too low for an immediate feeding of the slabs to a rolling plant. This is due to mechanical and metallurgical reasons. Besides, a wear will occur at the displaceable plate elements so that trouble is likely to arise, the sealing of the mold cavity is difficult, the mold must meet high requirements and it is doubtful whether the simultaneous solidification and deformation of the strand will not result in metallurgical faults.